Gas turbine ceramic regenerator

ABSTRACT

Gas conducting passages extend through the solid ceramic hub of a rotating disc type ceramic regenerator. An inorganic cement bonds the hub to the main heat transfer portion of the regenerator. The passages in the hub reduce thermal expansion differences between the hub and the main portion, reduce the rotating mass of the regenerator and increase gas flow and heat transfer. Small amounts of the material used to make the main heat transfer portion of the regenerator can fill the passages.

United States Patent Blech 1 51 July 25, 1972 [5 GAS TURBINE CERAMIC 2,977,096 3/1961 Evans 1 65/7 REGENERATOR 3,319,707 5/1967 Luedemann 165/8 [72] Inventor: Joab J. Blech, Oak Park, Mich. Primary Examiner Alben w. Davis, Jr

[73] Assignee: Ford Motor Company, Dearborn, Mich. An0rr'1eyJohn R. Faulkner and Glenn S. Arendsen [22] Flled: Oct. 29, 1970 ABSTRACT Appl. No.: 85,018

References Cited UNITED STATES PATENTS l/l967 Williams ..l65/8 X 6/1954 Trulss on et al. ..l65/9 Gas conducting passages extend through the solid ceramic hub of a rotating disc type ceramic regenerator. An inorganic cement bonds the hub to the main heat transfer portion of the regenerator. The passages in the hub reduce thermal expansion differences between the hub and the main portion, reduce the rotating mass of the regenerator and increase gas flow and heat transfer. Small amounts of the material used to make the main heat transfer portion of the regenerator can fill the passages.

3 Claims, 3 Drawing Figures Patented July 25, 1972 INVENTOR 70 45 .7. BZZCV/ ATTORNEYS GAS TURBINE CERAMIC REGENERATOR SUMMARY OF THE INVENTION The relatively recent ceramic regenerators for gas turbine engines traditionally have been made with a solid ceramic hub surrounded by the main gas conducting portion. Such hubs are necessary to distribute the mechanical forces generated by regenerator rotation. Cracks in the hub itself and the surrounding area of the gas conducting portion soon became a major problem, however. Attempts to eliminate the cracking problem by increasing hub size to further reduce the mechanical forces have been ineffective.

This invention is based on the discovery that the cracking problems result from thermal expansion differences between the hub and the porous gas conducting portion rather than from mechanical forces. These expansion differences are alleviated by providing gas conducting passages in the hub itself. The passages extend entirely through the hub in a direction parallel to the gas flow direction so that the walls of the passages assist in heat transfer. Alternatively, larger passages in the hub can be filled with the thin walled, gas conducting construction used to make up the main gas conducting portions of the regenerator. Inorganic adhesive bonds the hub to the main gas conducting portion of the regenerator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a sectioned elevation of a portion of a gas turbine engine showing a ceramic regenerator having gas conducting passages in its hub portion.

FIG. 2 is an exploded perspective view of the regenerator of FIG. 1.

FIG. 3 illustrates an alternate construction in which relatively large passages formed in the hub are filled with the material used to make the main gas conducting portion of the hub.

DETAILED DESCRIPTION Referring to FIG. I, a gas turbine engine containing the regenerator of this invention has an essentially elliptical metal outer housing that is open at the top of the regenerator portion. FIG. I is sectioned along the major diameter of the ellipse. A smaller inner housing 12 is located inside housing 10 and terminates a short distance from the opening thereof. Inner housing 12 comprises an outer cylindrical wall 14 divided diametrically by a wall 15 into two semicircular passages 16 and 17. Wall 14 forms an annular passage 13 between part of its circumference and outer housing I0.

A rubbing seal 18 having the same shape as housing 12 is located on top of housing 12 where the seal is restrained from circular movement by fitting ribs 20 on its underside into corresponding slots on the top of housing 12. A cross arm seal 22 rests on top of wall 15 and has its ends in contact with seal 18. A metal cap 24 fits on top of housing 10. Cap 24 has a diametrical wall 26 located directly above wall 15. Wall 26 divides the area under cap 24 into spaces 28 and 30.

A pivot pin 32 is mounted on the top of wall 15 and projects upwardly through a hole in sea] 22. Pin 32 serves as the rotational axis for a ceramic regenerator 34 that is mounted on top of seals 18 and 20. An annular metal ring gear 36 contacts the periphery of regenerator 34 through an elastomeric pad 38 or other torque transmitting member. Ring gear 36 meshes with a gear 40 that is driven by a shaft 42 connected to engine rotating components (not shown). Rotating torque applied to ring gear 36 is transmitted through pad 38 to rotate the regenerator 34. A D-shaped seal 44 rests on top of regenerator 34 where the seal surrounds space 30.

Regenerator 34 comprises a solid ceramic hub 46 and a ceramic gas conducting portion 48 (see also FIG. 2). Gas conducting portion 48 comprises a plurality of relatively narrow walls defining a plurality of closely adjacent gas conducting passages that extend through the regenerator. Hub portion 46 has a centrally located opening 50 adapted to receive pivot pin 32. Radially outward of opening 50 are a plurality of small gas conducting passages 52 that extend through hub 46 in a direction substantially parallel to opening 50. Passages 52 connect space 28 with passage 16 when on the left side of seal 44 or connect passage 17 with space 30 when on the right side of seal 44. The portion of seal 44 subtended by wall 26 covers the top of opening 50. A layer 54 of an inorganic adhesive bonds the outer circumference of hub 46 to the inner circumference of gas conducting portion 48.

During engine operation, relative cool compressed gases from the engine compressor flow upward through passage 13 and into space 28. The gases from space 28 flow through the left sector of regenerator 34 and through passage 16 to the engine combustion chamber and turbine wheel (not shown). Exhaust gases leaving the turbine wheel flow upward through passage 17, through the right sector of regenerator 34 and into space 30 which exhausts the gases from the engine. A small amount of the gases passing through the regenerator from space 28 to passage l6 flows through those passages 52 on the left side of seal 44. Similarly a small amount of the gases passing through the regenerator from passage I7 to space 30 flows through those passages 52 of the hub that are on the right side of seal 44. Passages 52 reduce the mass of hub 46 and produce a closer match between the thermal expansion characteristics of the hub and the gas conducting portion. Additionally the gases flowing through the passages maintain hub temperature at approximately the temperature of the adjacent area of portion 48.

The FIG. 3 construction uses a solid ceramic hub 46 having a plurality of large axial passages 60. Each passage 60 is filled with the thin walled, gas conducting ceramic material construction used to'make up the main gas conducting portion 48 of the regenerator. Such gas conducting ceramic material typically comprises alternating layers of straight and corrugated, thin walled ceramic such as that shown in U.S. Pat. No. 3,446,089 Stockton. Gas flow through the material in passages 60 reduces thermally generated stresses between the hub 46' and the main gas conducting portion 48 and also improves regenerator efficiency.

In'a typical automotive ceramic regenerator, hub 46 has a diameter of about 4 inches and a length of about 3 inches. Central opening 50 has a diameter of five-eighths inch. The number, size and spacing of passages 52 is determined empirically to provide desired expansion and gas flow characteristics. Typically, the total exposed facial area of the passages, i.e., the area exposed to spaces 28 and 30, constitutes about I0 percent of the hub face area. In hub 46 having the same exterior dimensions, about 6-8 passages 60 having a diameter of about one-half inch provide excellent results.

Thus this invention providesa rotary disc shaped ceramic regenerator that eliminates the serious hub failure difficulties encountered with previous ceramic regenerators. The invention also improves overall regenerator gas conduction and heat transfer properties.

I claim:

I. In a gas turbine engine, a rotary disc shaped heat exchanger for transferring heat from hot exhaust gases leaving the engine to relatively cool gases entering the engine comprising a ceramic hub portion having an outer surface and a concentrically located central opening, said hub portion including passage means extending axially through the hub for reducing its thermal expansion characteristics, said passage means containing a plurality of relatively narrow ceramic walls defining a plurality of closely adjacent passages for conducting gases substantially parallel to said central opening of the hub portion, and

a ceramic peripheral portion attached to the outer surface of said hub portion, said peripheral portion including a plurality of relatively narrow walls defining a plurality of closely adjacent passages for conducting gases substantially parallel to said central opening of the hub portion.

portion and conducting cool gases through the hub portion when on the other radial side of the hub portion.

3. The engine of Claim 2 in which the exposed facial area of the passages is about 10 percent of total hub facial area.

* I I III 

1. In a gas turbine engine, a rotary disc shaped heat exchanger for transferring heat from hot exhaust gases leaving the engine to relatively cool gases entering the engine comprising a ceramic hub portion having an outer surface and a concentrically located central opening, said hub portion including passage means extending axially through the hub for reducing its thermal expansion characteristics, said passage means containing a plurality of relatively narrow ceramic walls defining a plurality of closely adjacent passages for conducting gases substantially parallel to said central opening of the hub portion, and a ceramic peripheral portion attached to the outer surface of said hub portion, said peripheral portion including a plurality of relatively narrow walls defining a plurality of closely adjacent passages for conducting gases substantially parallel to said central opening of the hub portion.
 2. The engine of claim 1 in which said hub portion comprises a plurality of said passage means extending through said hub portion in a direction substantially parallel to said central opening, said passage means conducting hot exhaust gases through said hub portion when on one radial side of the hub portion and conducting cool gases through the hub portion when on the other radial side of the hub portion.
 3. The engine of Claim 2 in which the exposed facial area of the passages is about 10 percent of total hub facial area. 